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The mesic savannas of the Bateke Plateau: carbon stocks and floristic composition

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The Bateke Plateau in the Republic of Congo is one of the last frontiers for ecology, with little known about its floristics and physiognomy. Despite occupying 89,800 km² and its importance for local livelihoods, its ecology and ecosystem functions are poorly understood. Situated on Kalahari sands, the Bateke has a complex evolutionary history, mainly isolated from other savannas for much of its past, with currently unresolved ecological implications. Here, we assess the biomass and floristic diversity of this savanna. We established four 25-ha permanent sample plots at two savanna sites; inventoried all trees; assessed biomass and species composition of shrubs, forbs and grasses; and characterized the soils. Total plant carbon stocks (aboveground and belowground) were only 6.5 ± 0.3 MgC/ha, despite precipitation of 1600 mm/yr. Over half the biomass was grass, with the remainder divided between trees and shrubs. The carbon stock of the system is mostly contained in the top layer of the soil (16.7 ± 0.9 MgC/ha in 0–20 cm depth). We identified 49 plant species (4 trees, 13 shrubs, 4 sedges, 17 forbs, and 11 grass species), with an average species richness of 23 per plot. There is tree hyperdominance of Hymenocardia acida (Phyllanthaceae) and a richer herbaceous species composition dominated by Loudetia simplex and Hyparrhenia diplandra. The low carbon stocks and tree biodiversity, compared to other African savannas, are surprising considering the high rainfall. We speculate it is due to low nutrient soils, high fire frequency, and the effect of a temporally variable and restricted connection to the main southern African savanna complex. © 2018 The Authors. Biotropica published by Wiley Periodicals, Inc. on behalf of Association for Tropical Biology and Conservation
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The mesic savannas of the Bateke Plateau: carbon stocks and floristic composition
Paula Nieto-Quintano
1,5
, Edward T. A. Mitchard
1
, Roland Odende
2
, Marcelle A. Batsa Mouwembe
3
, Tim Rayden
4
,and
Casey M. Ryan
1
1
School of GeoSciences, University of Edinburgh, Crew Building, Edinburgh EH9 3FF, UK
2
Laboratoire de botanique et d’
ecologie, Facult
e des Sciences et Techniques, Universit
e Marien Ngouabi, BP 69, Brazzaville, Congo
3
Ecole Nationale Sup
erieure d’Agronomie et de Foresterie, Universit
e Marien Ngouabi, BP 69, Brazzaville, Congo
4
Wildlife Conservation Society, 2300 Southern Boulevard, Bronx, New York, USA
ABSTRACT
The Bateke Plateau in the Republic of Congo is one of the last frontiers for ecology, with little known about its oristics and physiog-
nomy. Despite occupying 89,800 km
2
and its importance for local livelihoods, its ecology and ecosystem functions are poorly under-
stood. Situated on Kalahari sands, the Bateke has a complex evolutionary history, mainly isolated from other savannas for much of its
past, with currently unresolved ecological implications. Here, we assess the biomass and oristic diversity of this savanna. We established
four 25-ha permanent sample plots at two savanna sites; inventoried all trees; assessed biomass and species composition of shrubs,
forbs and grasses; and characterized the soils. Total plant carbon stocks (aboveground and belowground) were only 6.5 0.3 MgC/ha,
despite precipitation of 1600 mm/yr. Over half the biomass was grass, with the remainder divided between trees and shrubs. The car-
bon stock of the system is mostly contained in the top layer of the soil (16.7 0.9 MgC/ha in 020 cm depth). We identied 49 plant
species (4 trees, 13 shrubs, 4 sedges, 17 forbs, and 11 grass species), with an average species richness of 23 per plot. There is tree
hyperdominance of Hymenocardia acida (Phyllanthaceae) and a richer herbaceous species composition dominated by Loudetia simplex and
Hyparrhenia diplandra. The low carbon stocks and tree biodiversity, compared to other African savannas, are surprising considering the
high rainfall. We speculate it is due to low nutrient soils, high re frequency, and the effect of a temporally variable and restricted con-
nection to the main southern African savanna complex.
Abstract in French is available with online material.
Key words: Bateke Plateau; carbon stocks; Republic of Congo; savanna; species composition.
THE BATEKE PLATEAU IS A SAVANNA-COVERED PLATEAU LOCATED
MAINLY IN THE SOUTHERN REPUBLIC OF CONGO, but also extending
into the east of Gabon and the southwest of Democratic Repub-
lic of Congo (DRC), and with an area of approximately
89,800 km
2
(Fig. 1). It comprises ve different savanna plateaus
(Koukouya, Djambala, Nsa, Ngo, and Mbe/Bateke), with an eleva-
tion that ranges from 259 to 872 m (mean of 545 m), each sepa-
rated by deep valleys (Descoigns 1960, Congo Basin Forest
Partnership, 2006). The landscape is located on the northern part
of the Kalahari sands, an ancient sand dune system (Haddon
2000), with soils that are mainly deep, sandy in texture and ferralitic
(Schwartz & Namri 2002), providing rapid drainage. There are also
some podzols in lower areas (Schwartz 1988). This area has a tropi-
cal transitional climate, characterized by an average annual rainfall
of 15001800 mm (obtained from Harris et al. 2014). There is a
main dry season from June to September and a short dry season in
January and February (Walters 2010b). The Bateke Plateau has his-
torically low human population densities, around 0.2 inhabitants/
km²(Congo basin forest partnership 2006). Bateke populations
mainly practice subsistence agriculture, gathering, shing, and hunt-
ing (Walters 2010a, Rayden et al. 2014). Agro-economic activities,
charcoal production, logging, hunting, and bushres have widely
impacted this landscape, driven by the demand from the large capi-
tal cities of Brazzaville and Kinshasa (populations of 1.8 and 9.5
million, respectively) (Hoare 2007).
The vegetation of the Bateke Plateau is predominantly a
mosaic of woody savanna and grasslands, with patches of closed
canopy forest, the latter conned to rivers and valley oors,
pockets at the top of hills, and surrounding settlements, where
there is greater water availability and protection from re (Duvi-
gneaud 1953b). The wooded savanna is dominated by an open
canopy of Hymenocardia acida Tul. (Phyllanthaceae) and Annona
senegalensis Pers. (Annonaceae) trees, with an understory of grasses
and locally endemic forbs (Walters 2012). The grasslands are typi-
cally dominated by Loudetia simplex and Hyparrhenia diplandra
(Duvigneaud 1953b).
The Bateke Plateau intrudes into the Congo Basin rainforest
and has a precipitation clearly suitable for closed canopy forest
establishment. Here, savanna and forest coexist under the same
Received 24 May 2018; revision accepted 26 July 2018.
5
Corresponding author; e-mail: paula.nieto@ed.ac.uk
ª2018 The Authors. Biotropica published by Wiley Periodicals, Inc. on behalf of Association for Tropical Biology and Conservation 1
This is an open access article under the terms of the Creative Commons Attribution License, which permits use,
distribution and reproduction in any medium, provided the original work is properly cited.
BIOTROPICA 0(0): 1–13 2018 10.1111/btp.12606
climatic and edaphic conditions with sharp transitions (Schwartz
et al. 1995). This has made it problematic to dene the origin of
this savanna, with conicting hypotheses as to the lack of tree
cover, which have important consequences for its conservation
(Veldman et al. 2014, 2015, Bond & Zaloumis 2016). Some
authors (Aubreville 1949, Duvigneaud 1953b, Elenga et al. 1994)
have suggested an anthropogenic origin, caused by the arrival of
human populations. Conversely, the weight of recent evidence
supports an origin caused by arid events in the past, though
humans could have played a role (Koechlin 1960, Aubreville
1962, Foresta 1990, Elenga et al. 1994, Schwartz et al. 1995, Vin-
cens et al. 1999, Oslisly et al. 2013). The recent climatic history of
the region is complex. There is evidence of a humid period with
mainly forests covering the region from 40,000 to 24,000 years
BP, followed by a drier period from 24,000 to 12,000 years BP
when herbaceous communities expanded (Dechamps et al. 1988,
Schwartz 1988, Elenga et al. 1994, Schwartz et al. 1995). From
12,000 years BP onwards, humid conditions encouraged new for-
est development (Dechamps et al. 1988, Elenga et al. 1994),
supported by studies suggesting that, as recently as 4000-
3500 years BP, the Bateke Plateau was forested (Dechamps et al.
1988, Schwartz et al. 1995, Vincens et al. 1999). These forests
were likely replaced by open grasslands around 3000 years BP,
when a major arid event occurred with greater seasonality, caus-
ing extension of grasses (Elenga et al. 1994, Schwartz et al. 1995,
Vincens et al. 1999, Maley 2001), and coincident with the arrival
of increased human populations (Schwartz 1992). However, even
during the most humid episodes of the past 40,000 years, there
is evidence that some savanna still existed in the area (Dechamps
et al. 1988, Vincens et al. 1999).
The Bateke belongs to the Guineo-Congolian center of
endemism (White 1983), with most of the Bateke being in the
Western Congolian forestsavanna mosaic ecoregion (Olson et al.
2001). These savannas have been fairly isolated from other
savanna formations, especially from West Africa by the Congo
Basin rainforest. In the Guineo-Congolian region (White 1979)
and in southern Kalahari areas, endemism is high (Walters et al.
2006), with many sand-adapted and pyrophytic species. This
FIGURE 1. Map of the study area, the Bateke Plateau, located mainly in the Republic of Congo. The left-hand map shows the extent of the Bateke Plateau
(red), the Kalahari sands (dashed), and the weather station of Gamboma used for the analysis of the temperature and precipitation data (yellow dot). The right-
hand panel shows the location of the Leni and Lesio Louna reserves, where the sampling plots were placed (red dots), over a Digital Elevation Model (DEM)
and the land use cover (GlobCover 2009, reclassied).
2 Nieto-Quintano, et al.
suggests potential for endemism in the Bateke, and indeed this is
supported by recent ndings (Bamps 2013). In Gabon, there
have been recent reports of more than 30 new plant records
from savannas, and six globally rare species restricted to Kalahari
sands or moist savannas (Walters et al. 2006, van der Maesen &
Walters 2011), and in South Congo, Koechlin (1960) found 12%
endemic species. However, Bateke savannas were considered by
White (1983) as secondary with some being edaphic and by
Schwartz et al. (1995) as inclusive or edaphic, and original, with-
out equivalent in the past. The theory of Bateke savannas being
secondary would contradict potential endemism, as secondary
savannas tend to have lower plant species richness and absence
of geoxylic suffrutices (Zaloumis & Bond 2016). Plant species
with a geoxylic suffrutex growth form are plants with large
woody underground structures and short-lived aerial shoots, with
a high capacity to resprout stimulated by re, thus providing an
alternative escape from re (White 1977). They are mainly ende-
mic to the Kalahari sands of the Zambezian region and occur
almost exclusively in higher rainfall savannas with frequent res
(White 1977, 1979, Revermann et al. 2017).
There is evidence from charcoal that res have occurred in
the Bateke since 2100 BP, and almost certainly they occurred fre-
quently far further back in time (Schwartz 1988, Walters 2012).
Nowadays, res are mostly anthropogenic, occurring mainly in
the dry season for hunting and gathering (Walters 2010a, 2012).
Frequent res, fueled by the continuous layer of grasses, have
unclear effects on species richness (Higgins et al. 2000, Smith
et al. 2013) and probably encourage specialization (Walters et al.
2006). Herbivore densities are low and do not cause much distur-
bance due to historic and current hunting, though there probably
were once high herbivore densities that could have shaped the
landscape (Walters 2010b).
BIOMASS STOCKS AND BOTANICAL STUDIES INTHE BATEKE
PLATEAU.Savannas cover around half of the African continent
(Menaut 1983), but despite their importance to the global carbon
cycle, current knowledge of African savanna biomass stocks and
oristic diversity is limited (Hall & Scurlock 1991), especially in
the understudied ecosystems of the Bateke Plateau.
We searched and collated the published and gray literature
of the Bateke to provide a rst comprehensive review of the bio-
mass stocks in the Plateau and found eight studies that have pre-
viously quantied some aspects of biomass stocks of these
savannas (Makany 1973, Apani 1990, Schwartz & Namri 2002,
Yoka et al. 2010, 2013, Gigaud 2012, Lokegna 2015, Ifo 2017).
These values are in general low for African savannas. There have
been still fewer estimates of soil carbon stocks in the Bateke Pla-
teau (Namri 1996, Schwartz & Namri 2002, Ifo 2017). The spa-
tial scale of all these studies is restricted, and none have assessed
all ecosystem carbon storage elements together, limiting their abil-
ity to provide understanding of the system.
We have better knowledge of the plant species of the region,
with oristic inventories of Gabon (Aubreville 1961) and DRC
(Robyns 1949), and a Checklist for Gabon (Sosef 2006). In RoC,
there is a published inventory for the vascular ora of the Republic
of Congo (Sita and Moutsambote (1988)), which provides a list of
4397 species (198 families and 1338 genera), but with the vast
majority being forest species and no indication of their distribution.
This inventory has been slightly updated since then, with 84 species
added by Champluvier and Dowsett-Lemaire (1999), and 64 by
Lachenaud (2009). More usefully, there is an illustrated list of plants
of the Lesio Louna and Leni reserves, which are major reserves
covering 6% of the Bateke Plateau, that list 457 species belonging
to 119 families (Nsongola et al. 2006). Some old botanical studies
in French of this landscape also exist, but they are limited to the
South of the Bateke (Koechlin 1960, Descoigns 1972), the Cuvette
region (Descoigns 1960, Yoka et al. 2013), and the Teke Plateau
(Makany 1973, Apani 1990), and in more recent some mastersthe-
ses (Lokegna 2015, Mampouya 2015). However, all these studies
are limited in scope, contributing to the Republic of Congo being
one of the botanically least known and inventoried countries in
tropical Africa (Lachenaud 2009, Sosef et al. 2017).
Due to the lack of basic data on this ecosystem, it is difcult
to understand its function, conservation value, and the transfor-
mations it could undergo with climate change and management
changes. Our main objective was to characterize the structure of
the vegetation and oristic diversity of the Bateke Plateau using
data collected from four very large (25-ha) inventory plots,
located within two protected areas and designed as a long-term
re experiment. Our research questions were as follows: (1) What
is the carbon storage of our two woody savanna study sites, and
how is it distributed between vegetation and the soil? (2) What is
the species diversity of the study sites, and how does diversity
vary by plant life form type? (3) Can we explain the structure of
these savannas in the context its biogeographical history and
human inuence?
Due to frequent res and intermediate rainfall, we expected
these savannas to have a low tree biomass but higher grass bio-
mass and understory diversity, with the presence of pyrophytes
and geoxylic suffrutex species. Moreover, if these savannas are
ancient as recent evidence suggest, with a uctuating savanna/
forest cover for at least past 40,000 years, and because of its geo-
graphical position, we would anticipate high plant and forb diver-
sity, presence of geoxylic suffrutex, and some endemism. We
would expect oristic similarities with the southern savannas due
to the Kalahari sands acting as a corridor.
Overall, we provide a baseline biomass and diversity inven-
tory for these savannas that we hope will be useful to other sci-
entists interested in their structure and function, and assist with
their management and conservation.
METHODS
SITE DESCRIPTION.We conducted the study in two protected areas
in the Bateke Plateau, the Leni and the Lesio Louna reserves
(Fig. 1), situated about 160 and 110 km north of Brazzaville,
respectively. These sites have a precipitation of 1627 to 1966 mm/
yr and a mean annual temperature of approximately 25°C (all cal-
culated for the period 19962016 from data of Climate Research
Unit (CRU) for the station of Gamboma (Harris et al. 2014), see
Carbon and Floristics of the Bateke Plateau 3
Fig. 1 for location). The Leni Wildlife Reserve (LWR) has a total
area of 5010 km
2
(IUCN & UNEP 2015) and was established in
1951 as a hunting reserve. The Lesio Louna Reserve (LLR) has a
total area of 1730 km
2
and was established in 1993 as a sanctuary
for the reintroduction of orphan gorillas by the Aspinall Founda-
tion and later as a Natural Reserve in 1999. Both reserves are listed
as IUCN Category IV and aim to maintain, conserve, and restore
species and habitat (IUCN & UNEP 2015). They feature typical
Bateke habitats: rolling hills studding a plateau dissected by river
valleys, with open savanna dominating, and with forest patches
around rivers and on the top of hills.
CARBON STOCK ASSESSMENT.We established four 25-ha perma-
nent sample plots (500 m 9500 m) in the savanna, two in each
protected area, in the year 2015 as part of a long-term re exper-
iment (plots LWR1 and LWR2 in Leni and plots LLR1 and
LLR2 in Lesio Louna). The plots were not randomly located,
selected to be in wooded savanna, easily reachable by foot from
research camps, and sufciently large to encompass much of the
natural variability of the savannas. All four plots were located
with one edge running about 30 m away from the edge of closed
canopy forest, associated with nearby rivers. Data collection took
place in 2015 in the beginning of the dry season (May/June) for
plots LWR2 and LLR1 and in the end of the dry season
(September/October) for plots LWR1 and LLR2.
In these plots, we inventoried all living trees with a diameter
at breast height (dbh) greater than 10 cm, recording: species,
dbh, height, status (alive/dead, standing/fallen, and broken), and
spatial location (by GPS). Dbh was measured at 1.3 m height
aboveground, and if the tree forked below this, each stem was
measured independently and treated as different trees. Trees were
identied to species level by Roland Odende, and their height
was estimated using a Nikon Forestry Pro Laser.
For the estimation of the aboveground biomass (AGB) from
these measurements, we used the generic pan-tropical allometric
equation from Chave et al., (2014) with wood density obtained
from the Wood Density Database (Chave et al. 2009, Zanne et al.
2009) based on the species determination. This was considered
the most appropriate for the study site as there are no locally
dened allometric equations for this location. As height was esti-
mated individually on the ground for every tree, there was no
need to use diameter measurements to estimate tree height
through a locally derived or regional relationship. However, we
did compare dbh and height values in order to test the strength
of this relationship in this ecosystem and to develop a model for
use by others. Belowground tree biomass (BGB) was not mea-
sured in the eld, but estimated using a root-to-shoot ratio
(R:S =0.42) described by Ryan et al. (2011) for miombo woodlands.
We consider this equation was appropriate as the trees are subject to
similar ecological pressure and constraints, and due to the absence of
a local equation or one for Central African savannas.
To survey grasses and saplings/shrubs, the latter dened as
woody plants with a dbh <10 cm and with a diameter at 10 cm
aboveground (D
10
) greater than 1 cm, 16 permanent circular
subplots with a radius of 4 m (50.3 m
2
) were established within
each plot, on every 100 m vertex, as shown in Fig. 2. In these
subplots, saplings were tagged; measured (D
10
) using a calliper,
height, and dbh where applicable; and identied to species level.
To estimate the biomass of the saplings (stems and roots), the
allometric equations from Ryan et al. (2011) were applied for sap-
lings with dbh <5 cm.
SBs ¼0:0007645 D102þ0:004645 D10 þ0:03876 (1)
SBr ¼0:001784 D102þ0:0001413 D10 þ0:15839 (2)
where, SBs and SBr is the stem and root wet sapling biomass in
kg, respectively. This was converted to biomass Mg/ha using the
dry mass fraction (DMF) of 0.61 determined in the same study.
For saplings with D
10
5 cm and dbh <10 cm, the Chave et al.
(2014) Equation 1 was used for the AGB, and the ratio R:
S=0.42 for roots.
Grass biomass was measured using a disc pasture meter
(DPM) (Bransby & Tainton 1977, Dorgeloh 2002), by taking four
measurements at each subplot (therefore 64 measurements per
25-ha plot). The DPM was calibrated in each plot before its use. In
order to perform this calibration, all the grass under the DPM was
cut and weighed (wet weight). A subsample of grass was weighed,
then dried to the point of no further weight loss, and re-weighed in
order to determine dry mass based on percentage moisture loss
from the samples. The relationship between mean disc settling
heights (cm) and grass biomass per quadrat was determined sepa-
rately for each plot using linear regression (linear calibration curve,
N=3540 for each plot, r
2
=0.350.75). BGB was not measured
in the eld, but it was estimated using the ratio calculated by Apani
(1990) for grasses in the Teke Plateau (R:S =2.5).
Biomass was converted into carbon stocks using a conver-
sion factor of 0.47 (Ryan et al. 2011) for woody plants and 0.42
for grasses (Ryan 2009). All biomass values are given in metric
tonnes of carbon per ha (MgC/ha).
SOIL ANALYSIS.Soil analysis was performed in Plot LWR2
(Leni) and LLR1 (Lesio Louna), by taking two soil samples
(4 m apart) in each subplot located in the transects numbered 2
and 4 (Fig. 2), at two different horizons, h0 (05 cm) and h1 (5
20 cm), giving 32 soils samples per plot. Samples were dried,
sieved, and analyzed in the physiochemical laboratory of the
Institut de Recherche en Sciences Exactes et Naturelles (IRSEN)
at Pointe-Noire, in order to determine total organic carbon, nitro-
gen content, and bulk density (measured with a cylinder core to
assess the volume of the soil and determine the weight after dry-
ing, (Blake & Hartge 1986) (Batsa et al. (2017).
SPECIES COMPOSITION.We performed a survey of the oristic
composition by identifying all plant species within the subplots
(presence/absence), rst in situ, and where not possible samples
were taken to the National Herbarium of IRSEN for identica-
tion, as described in Odende (2016). For six species, the identi-
cation was only possible to genus level. For the species
4 Nieto-Quintano, et al.
nomenclature, the Sita and Moutsambote (1988) ora inventory
and the Plant list data base (The Plant List, 2013) were used.
Species were further categorized into the different life forms
(trees, shrubs, sedges, forbs, and grasses). To further categorize
shrubs and trees as geoxylic suffrutex, we used the denition of
White (1977) as plants with a massive, woody, underground axes
but only annual or short-lived shoots aboveground, and use the
list provided in (Maurin et al. 2014). Species diversity was calcu-
lated using species richness for all presence/absence data, as the
total number of unique species observed in each subplot.
DATA ANALYSIS.We investigated the within-plot variances using
linear models and one-way analysis of variance (ANOVA). To
evaluate to what extent species were well sampled, we con-
structed rareed species accumulation curves. Dissimilarity in
species composition between sites (beta diversity) was calculated
using Sørensen dissimilarity index. Compositional patterns were
visualized using a non-metric multidimensional scaling (NMDS),
and correlations between the oristic composition and environ-
mental characteristics were assessed with multiple regression, by
tting the ecological variables to ordination scores using the en-
vtfunction of the vegan package (Oksanen et al. 2013).
All data analyses were performed using the R statistical soft-
ware v. 3.1.3 (R Core Team, 2015, http://cran.r-project.org),
using the vegan (Oksanen et al. 2013), spatstat (Baddeley &
Turner 2005), pgirmess (Giraudoux 2017), and iNEXT (Hsieh
et al. 2016) packages.
RESULTS
BIOMASS STOCKS.In total, we inventoried 4120 live tree stems
with a dbh 10 cm in our 100 hectares eld plots
(LWR1 =726, LWR2 =1480, LLR1 =1022, and LLR2 =892),
with a maximum dbh of 39.3 cm. The tree, grass, and saplings/
shrubs carbon stocks on a plot basis are summarized in Table 1,
with a mean total of 6.47 0.33 MgC/ha. Grass carbon stocks
were in general about equal to that of tree, shrub, and sapling
biomass combined, though there was considerable variation both
within and between plots. Plots had signicantly different above-
ground biomass for trees (ANOVA single factor, P<0.05) and
grasses (P<0.01).
Approximately 90% of the tree AGB was stored in trees
with a dbh between 10 and 22 cm, with large stems rare (Supple-
mentary Information Fig. S1). The stem density of the plots var-
ied from 29.0 (plot LWR1) to 59.2 tree stems per hectare (plot
LWR2) (Fig. S2).
SOIL CARBON AND NITROGEN.The mean bulk density of the 0
20 cm horizon was 1.48 0.01 Mg/m
3
(LWR2) and
1.44 0.01 Mg/m
3
(LLR1) (soil analysis results summarized in
Table S1). Carbon stocks and the C:N ratio were very low
in both sites. Soil carbon content estimations were very similar in
both proles, being slightly higher in the h0 prole than in the
h1, with an average of 16.74 MgC/ha. Carbon stocks and C:N
ratios were not signicantly different between sites (ANOVA sin-
gle factor, P>0.05).
We also found that dbh was a predictor of tree height,
although with a weak positive relation (R
2
=0.14, P<0.001) in
all plots (see Fig. S3 for graph and equation). Ninety percent of
the inventoried trees with a dbh 10 cm were taller than 3.1 m.
SPECIES CHARACTERIZATION.We identied 49 species in total (4
trees, 13 shrubs, 4 sedges, 17 forbs, and 11 grass species). A
complete list of the species is given in the Supplementary Infor-
mation (Table S2). For trees, Hymenocardia acida Tul. (Phyllan-
thaceae) was hyperdominant, comprising 93.8% of the
FIGURE 2. Sampling method. Plots were 500 9500 m (25 ha), with subplots placed every 100 m. Each subplot had a radius of 4 m in which grass and soil
(transects 2 and 4 only) measurements were taken.
Carbon and Floristics of the Bateke Plateau 5
inventoried stems across all plots (Table S3 in Supplementary
Information). There were 27 species common to both sites, 3
unique to Leni, and 11 unique to Lesio Louna. The Sørensen
index of dissimilarity between the two sites was 0.21, which indi-
cates a 21% dissimilar species composition between sites. The
most abundant grass species in all subplots was Loudetia simplex
and Hyparrhenia diplandra. Poaceae was the dominant family across
the plots, followed by Fabaceae and Cyperaceae. Fig. 3A summa-
rizes the number of species per plot divided into vegetation types.
Species richness was similar for all plots (LWR1 22, LWR2 25,
LLR1 29, and LLR2 23), with a mean of 25 3. There is a high
presence of woody species with a geoxylic suffrutex growth form
(Table S2), and the understory is more diverse.
The rareed species accumulation curves (Fig. 3B) are com-
parable among the plots. The estimated sample completeness was
for plot LWR1 96%, LWR2 99%, LLR1 93%, and LLR2 97%.
When comparing diversity at the subplot level, NMDS ordination
showed dissimilarity of the two sites in relation with the species
composition of the subplots, but little difference between the two
plots within each site (Fig. 4). Variation in species composition is
best explained by the distance to forest, elevation, and tree and
grass aboveground biomass (NMDS, P<0.05).
DISCUSSION
CARBON STOCKS AND COMPARISON WITH OTHER STUDIES.At our
two sites, the average total vegetation carbon stocks (above-
ground and belowground) was 6.5 MgC/ha, with the topsoil
horizon (020 cm) holding over twice as much, 16.8 MgC/ha
(Fig. 5, and considerably more carbon likely stored at deeper
depths not investigated here).
The climate of the Bateke Plateau, with annual rainfall of
~1600 mm and an intense 34-month dry season, would suggest
a closed canopy forest in the absence of disturbances (Sankaran
et al. 2005). Tree cover generally increases with rainfall, but re is
an important disturbance in areas with intermediate precipitation
(Staver et al. 2011). On Kalahari sands, there is also a gradient of
increasing woody cover and biomass with increasing precipitation,
at least in the southern section (Scholes et al. 2002). Conse-
quently, although we would expect the Bateke to have a high
woody cover and tree density, the observed low biomass could
be the product of frequent res, which reduce woody cover and
maintain the grasslands (Favier et al. 2004, Staver et al. 2011),
and the sandy soils, which are poor in organic matter and nutri-
ents (Yoka et al. 2010) and have a high percolation rate. The high
precipitation favors grass productivity, providing more fuel for
res. Savannas with sandy nutrient-poor soils are more likely to
favor woody over herbaceous cover (Scholes 1990, Sankaran et al.
2005, Bond 2008), although the edaphic conditions can also be a
restriction for trees (Mills et al. 2013). Tree seedlings compete
with grasses for water and nutrients belowground (Scholes &
Archer 1997), but disturbances are the main determinants for
trees not attaining the maximum woody cover established by
water availability (Mills et al. 2013).
Although these carbon stock values appear low for savannas,
they are not unusual for the Bateke (Table 2). The tree biomass
estimated in this study is between the values obtained by Apani
(1990) for the Teke Plateau and by Gigaud (2012) for the DRC.
Grass biomass is also similar to that calculated by Yoka et al.
(2013) for the South of RoC and to Makany (1973), but is lower
than some other studies (Apani 1990, Yoka et al. 2010). This
could be due to the timing of the sample collection, which were
later in the year than the likely time of maximal grass biomass,
around May at the end of the main wet season (Apani 1990,
Yoka et al. 2010). In the Kalahari sands, Scholes et al. (2002)
found that grass biomass increased with higher precipitation up
to 600 mm and then decreased due to competition with trees (up
to 1000 mm). This does not appear to be the case in our two
TABLE 1. Summary of the average carbon stocks per hectare (MgC/ha). For grasses and saplings/shrubs, indicates the standard error per plot of 16 950.3 m
2
subplots; and for
tree stems, it is the standard error of 25 91 ha subplots.
Biomass stock (MgC/ha)
MeanLWR1 LWR2 LLR1 LLR2
Grasses
Stems 0.67 0.11 2.26 0.09 1.39 0.07 0.58 0.04 1.22 0.09
Roots 1.69 0.27 5.65 0.23 3.47 0.16 1.45 0.09 3.06 0.23
Grasses Total 2.34 0.29 7.91 0.25 4.86 0.18 2.03 0.10 4.28 0.25
Saplings/Shrubs
Stems 0.52 0.13 0.66 0.34 0.64 0.28 0.26 0.10 0.52 0.12
Roots 0.86 0.44 0.57 0.52 0.71 0.70 0.53 0.28 0.63 0.13
Saplings Total 1.38 0.24 1.23 0.42 1.36 0.43 0.79 0.30 1.15 0.18
Trees
Stems 0.42 0.09 1.01 0.11 0.77 0.16 0.68 0.07 0.74 0.06
Roots 0.18 0.04 0.42 0.05 0.32 0.07 0.24 0.03 0.29 0.02
Trees Total 0.60 0.10 1.42 0.12 1.10 0.17 0.92 0.07 1.03 0.07
Total 4.33 0.41 10.57 0.52 7.31 0.51 3.74 0.32 6.47 0.33
6 Nieto-Quintano, et al.
sites, but further research about treegrass competition is needed
to better understand this system.
The biomass of saplings/shrubs was higher than might be
expected from a visual assessment, which suggests a landscape
dominated by grass and scattered trees. The density of shrubs in
this landscape was very patchy, and the subplot density measure-
ments have a non-normal, right-skewed distribution, with many
plots not having any shrubs, and some containing high densities.
Larger or more subplots would be required for a more robust
shrub biomass estimation.
FIGURE 3. (A) Number of species per plot by type (trees, shrubs, sedges, forbs, or grasses) and total. (B) Rareed species richness showing the cumulative num-
ber of species observed and an extrapolated sampling curve (dashed line) of subplot species for all plots (N =16 subplots per plot) and for all combined
(N =64).
FIGURE 4. Non-metric multidimensional scaling (NMDS) ordination for all the oristic data (grass and woody plants). Big circles grouping the sites (Lesio
Louna [LLR] and Leni [LWR]), ll circles grouping the subplots (LWR1, LWR 2, LLR1, and LLR2), with condence limit for ellipses of. 0.95. Floristic composi-
tion was correlated with environmental vectors, displayed as arrows (where P <0.05, and *where P <0.01). Elevation (m) =elevation relative to lowest point in
each plot.
Carbon and Floristics of the Bateke Plateau 7
Few studies have quantied the BGB in the Bateke, but our
results are similar to those obtained by Apani (1990) for grasses
and Lokegna (2015) for trees. These values (mean) are low
compared to reported general tropical savannas root biomass,
such as the 6.48 MgC/ha reported by Jackson et al. (1996) for
tropical grassland savannas. Tree, shrub, and grass BGB were
estimated with ratios found in the literature, and therefore, having
local allometric equations would provide better estimates. More-
over, we might have underestimated by using the mean root-to-
shoot ratio described by Ryan et al. (2011), as this ratio varied
from 0.27 to 0.58. The BGB of the geoxylic suffrutex species will
have been underestimated as they contain disproportionately large
underground structures.
Our savanna plots were characterized by a very low tree
stem density (averaging 41.2 stems per ha) and low biomass, con-
sistent with systems with high disturbance. This result indicates
the importance of using large (>10 ha) plot areas for the inven-
tory of this biome, as savannas are highly heterogeneous. How-
ever, in order to capture all landscape variability, larger scales of
sampling would be needed (Staver 2017).
The topsoil contributes the most to the carbon pool in our
plots (16.7 MgC/ha, 53% of the total), in concordance with other
studies of savannas (Scurlock & Hall 1998, Ciais et al. 2011), and
the low carbon density of these soils is similar to other studies in
Kalahari sands (Bird et al. 2004). Soil carbon stocks are similar to
those found in other studies of the Bateke Plateau (Table 2), such
as Ifo (2017), and slightly lower than Schwartz and Namri
(2002). Additionally, these values are much lower than in miombo
woodlands, where the median soil C stocks (030 cm) were 35.9
tC/ha, but supporting a much higher aboveground woody bio-
mass of 28.7 tC/ha (Ryan et al. 2016). Carbon content estima-
tions were very similar in both proles, being slightly higher in
the h0 prole than in h1. These carbon stock estimations are
important for further studies, to inform conservation measures
and in the design of more effective data collection protocols.
SPECIES DIVERSITY AND COMMUNITY COMPOSITION.The oristic
inventory results are in concordance with those of other authors
for the Bateke (Duvigneaud (1953a), Makany (1973) and Nson-
gola et al. (2006)). Most of the tree species inventoried are typical
of dry savannas (Duvigneaud 1949). Many authors in fact
denominate this type of savanna of the Bateke as Hymenocardia
savanna (Duvigneaud 1953a, Descoigns 1972, Makany 1973),
dominated by Hyparrhenia diplandra or by L. simplex (e.g., Makany
1973, Walters et al. 2013). H. acida, is a deciduous, re-tolerant
(Trapnell 1959), small tree that occurs in tropical African savan-
nas mainly on sandy, loamy, or clayey soils (Duvigneaud 1949). It
reproduces asexually through production of resprouts, stimulated
by frequent res (Walters 2012). Koechlin (1960) described that
he never saw a H. acida seedling in the area, which implies the
FIGURE 5. Representation of the average carbon stocks (MgC per hectare) for all the plots in the study sites. Soil is Soil Organic Carbon (SOC) stock.
8 Nieto-Quintano, et al.
importance of vegetative reproduction (Walters 2007). Boaler and
Sciwale (1966) found for miombo woodlands that H. acida was
one of the fastest growing trees, therefore potentially making
them grow quickly enough to escape mortality by re in places
given enough precipitation, like in the Bateke. These characteris-
tics of H. acida could explain its hyperdominance in this system.
In our inventory, we found six shrubs and trees with a
geoxylic suffrutex growth form (Table S1), indicating a pyro-
phytic component of the ora and potentially an established
savanna in a climate suitable for forests (White 1977, Walters
et al. 2006, Maurin et al. 2014). We have also found some Cyper-
aceae species, which often occupy recently burned grasslands, and
some pyrophytes, including H. acida, A. senegalensis, Bridelia ferrug-
inea, Psorospermum febrifugum, and Maprounea africana (Walters et al.
2006), which highlights the importance of re in maintaining
these ecosystems. Fire is likely responsible for maintaining the
forestsavanna mosaic with abrupt boundaries between forest
and savanna areas. We did not nd savannaforest transition spe-
cies found in similar habitats, like Walters et al. (2006) in Gabon,
perhaps indicating the savanna at our sites has been stable for
some time.
The species diversity we found is quite low compared to
other African savannas, for example in South Africa (Fynn et al.
2004, Smith et al. 2016) and for miombo woodlands (Masocha
et al. 2011). The species richness is more comparable to values
obtained for natural grasslands in South Africa, and greater than
those for any secondary grasslands (Zaloumis & Bond 2016),
suggesting these savannas are not new and probably have existed
as a mosaic for long time. We also did not nd any endemic spe-
cies in our inventory, with most of them having wider distribu-
tions in Africa. However, we only subsampled 100 ha of
savanna, from two sites located only 86 km apart, so our conclu-
sions about plant diversity cannot be assumed to apply to the
whole plateau. In Gabon, Wieringa and Sosef (2011) found for
the Bateke Plateau National Park a relatively unique ora with a
limited spatial extent, and Walters et al. (2006) encountered more
endemism in forests than in savannas. Although the Bateke
belongs to the Guineo-Congolian regional center of endemism
(White 1983), some studies had found species distributions simi-
lar to other regions. Walters et al. (2006) concluded in their analy-
sis about oristics in the Gabons Bateke Plateau that over 50
percent of the species were classied as Guineo-Congolian, but
20 percent had extended distributions into the Zambezian or
Sudanian phytochoria, and that sites on Kalahari sands in Gabon
shared oristic afnities with Leni. Similarly, Koechlin (1960)
determined for the Kalahari sand savannas in the south of RoC
that 12% of the species were endemic and 55% had a Sudano-
Angolan distribution (Walters et al. 2006). Duvigneaud (1953a)
described the Kalahari plateau in the DRC (Kwango) as an inter-
mediate zone, with a Guineo-Congolaise climate but with Zam-
bezian elements due to the edaphic conditions. Additionally,
Fayolle et al. (2018) concluded, using the data presented here, that
Leni and Lesio Louna have oristic similarities with Northern
and Western African savannas and woodlands. The mixed oris-
tic composition of the Bateke is likely due to its historical spatial
geography. These savannas have been fairly isolated from other
savanna formations, with only some exceptions. The oristic
afnities with the south and east could be explained by a connec-
tion via a savanna corridor with the Angolan highlands (Fayolle
et al. 2018) and by the Kalahari sands sheets, which could have
provided a connection with southern species, although this
hypothesis remains uncertain (Walters et al. 2006). The similarities
with the northern savannas could be explained by the fragmenta-
tion of the Congo Basin forest during the Last Glacial Maximum
(18000 years ago) (Maley 1991, Fayolle et al. 2018). Furthermore,
the Sangha River Interval provided a large savanna corridor con-
necting the Sudanian savannas in the north to the Bateke savan-
nas (Maley 2001, Maley & Willis 2010, Bostoen et al. 2015).
TABLE 2. Allocation of carbon stocks (MgC/ha) in the Bateke Plateau savannas from different studies.
Grasses (MgC/ha) Trees (MgC/ha)
Soil (MgC/ha) AreaRoots Stems Roots Stems
Makany (1973) 1.39
(1)
1.71
(2)
Plateaux Teke RoC
Apani (1990) 4.31 1.78 0.17
a
Plateaux Teke RoC
Gigaud (2012) 1.66
a
Bateke DRC
Lokegna (2015) 1.85
a
Bateke (Mah) RoC
Yoka et al. (2010) 1.72
(1)
4.79
(2)
Cuvette RoC
Yoka et al. (2013) 1.18
(1)
2.63
(2)
Cuvette RoC
Schwartz and Namri (2002) 1520 (010 cm)
86102 (0100 cm)
b
Bateke RoC
Ifo (2017) 13.28 (020 cm)
45.95 (0100 cm)
Lesio Louna RoC
This study 3.06 0.23 1.22 0.09 0.29 0.02 0.74 0.06 16.74 0.9 (020 cm) Leni/Lesio Louna RoC
Notes:
(1)
Loudetia simplex
(2)
Hyparhenia diplandra.
a
Trees and shrubs.
b
Average of the Bateke land unit.
Carbon and Floristics of the Bateke Plateau 9
CONCLUSION
Our results show that the Bateke savannas store only small quan-
tities of carbon per hectare, with the largest pools in the soil and
roots. Its species diversity is low, and we found no evidence of
endemism. The savanna ecosystem is clearly controlled by re,
with all plants showing adaption to regular burning. We have fur-
ther shown the need to use large plots (>10 ha) to capture varia-
tions in carbon stocks and species diversity in this area. These
data will thus inform future studies on optimal sampling method-
ologies and carbon dynamics in this ecosystem. Our results,
although only representative of part of the Bateke, will further
help in understanding the complex relationship between grasses,
understory plants, trees, re, and resources. However, more stud-
ies are needed in this ecosystem to inform conservation and
restoration, particularly with regard to re regime, and to under-
stand future challenges from climate change.
ACKNOWLEDGMENTS
Funding for this work was provided by the US Forest Service
(USFS) and the University of Edinburgh. We thank USFS and
Wildlife Conservation Society-Congo (WCS) for providing logis-
tics and institutional support. We thank numerous eld assistants
(Roland Odende, Marcelle Armande Batsa Mouwembe, Ledia
Bidounga, and Onesi Samba) and ecoguards of Leni and Ibou
Briko, Prime Mobie and Denis Ngatse, for their invaluable help
and knowledge; Mr. Gilbert Nsongola for helping with the spe-
cies identication; and the people of Mpoh and M^ah for main-
taining the rebreaks and for sharing their knowledge about re
use. Edward T. A. Mitchard and Casey M. Ryan were supported
by the NERC-funded Socio-Ecological Observatory for the
Southern African Woodlands (NE/P008755/1).
DATA AVAILABILITY
Data used in this study are archived at the Dryad Digital Reposi-
tory: doi.org/10.5061/dryad.2122768 (Nieto-Quintano et al. 2018).
Information on using the vegetation data prior to the end of the
embargo can be found at seosaw.github.io.
SUPPORTING INFORMATION
Additional supporting information may be found online in the
Supporting Information section at the end of the article.
TABLE S1. Soil characteristics of Leni and Lesio Louna.
TABLE S2. Species composition list (presence/absence data) for all
subplots.
TABLE S3. Stem species number per plot for all trees.
FIGURE S1. AGB and cumulative sum of AGB vs. dbh
classes for all plots for trees.
FIGURE S2. Density of stems per hectare for all plots, with
box and whisker data based on individual values for the
25 91 ha subplots within each 25 ha plot.
FIGURE S3. Dbh vs Height for all trees in all plots, with
point density.
LITERATURE CITED
APANI, E. 1990. Contribution aletude phytoecologique de la savane a Loude-
tia demeusei et Hymenocardia acida des contreforts des Plateaux Teke
(Republique Populaire du Congo). PhD Dissertation. Universitede
Rennes.
AUBREVILLE, A. 1949. Climats, for^ets et desertication de lAfrique tropicale.
Societededitions geographiques, maritimes et coloniales, Paris. p. 351.
AUBR
EVILLE, A. 1961. Flore du Gabon. France, Paris.
AUBR
EVILLE, A. 1962. Savanisation tropicale et glaciations quaternaires. Adan-
sonia 2: 1684.
BADDELEY, A., AND R. TURNER. 2005. spatstat: An R Package for Analyzing
Spatial Point Patterns. J. Stat. Softw. 12: 142.
BAMPS, P. 2013. A new species of Kalaharia (Lamiaceae) from Central Africa.
Plant Ecology and Evolution 146: 134137.
BATSA, M. A., S. A. IFO,S.BINSANGOU,AND F. KOUBOUANA. 2017. Variabilite
spatiale des stocks de carbone organique du sol des savanes dans les
reserves de Lesio-Louna et de Leni, plateaux Tekes, Republique du
Congo. Afrique SCIENCE 13: 297307.
BIRD, M. I., E. M. VEENENDAAL,AND J. J. LLOYD. 2004. Soil carbon inventories
and d13C along a moisture gradient in Botswana. Glob. Change Biol.
10: 342349.
BLAKE,G.R.,AND K. H. HARTGE. 1986. Bulk density. Soil Science Society of
America, Madison, WI.
BOALER,S.B.,AND K. C. SCIWALE. 1966. Ecology of a Miombo Site, Lupa
North Forest Reserve, Tanzania: III. effects on the vegetation of local
cultivation practices. J. Ecol. 54: 577587.
BOND, W. J. 2008. What limits trees in C4 grasslands and savannas? Annu.
Rev. Ecol. Evol. Syst., 39: 641659.
BOND,W.,AND N. P. ZALOUMIS. 2016. The deforestation story: Testing for
anthropogenic origins of Africasammable grassy biomes. Philos.
Trans. R. Soc. Lond. B Biol. Sci. 371: 20150170.
BOSTOEN, K., B. CLIST,C.DOUMENGE,R.GROLLEMUND,J.M.HOMBERT,J.K.
MULUWA,AND J. MALEY. 2015. Middle to late holocene paleoclimatic
change and the early bantu expansion in the rain forests of Western
Central Africa. Current Anthropology 56: 354384.
BRANSBY,D.I.,AND N. M. TAINTON. 1977. The disc pasture meter: Possible
applications in grazing management. Proceedings of the Annual Con-
gresses of the Grassland Society of Southern Africa 12: 115118.
CHAMPLUVIER,D.,AND F. DOWSETT-LEMAIRE. 1999. Vascular plants from
Odzala National Park: Commented list of species new for Congo-
Brazzaville. Syst. Geogr. Plants 69: 928.
CHAVE, J., D. COOMES,S.JANSEN,S.L.LEWIS,N.G.SWENSON,AND A. E.
ZANNE. 2009. Towards a worldwide wood economics spectrum. Ecol.
Lett. 12: 351366.
CHAVE, J., M. RÉJOU-MÉCHAIN,A.BÚRQUEZ,E.CHIDUMAYO,M.S.COLGAN,W.
B. C. DELITTI,A.DUQUE,D.WELINGTON,P.M.FEARNSIDE,R.GOOD-
MAN,M.HENRY,A.MARTÍNEZ-YRÍZAR,W.MUGASHA,H.MULLER-
LANDAU,M.MENCUCCINI,B.NELSON,A.NGOMANDA,E.NOGUEIRA,E.
ORTIZMALAVASSI,R.PÉLISSIER,P.PLOTON,C.RYAN,AND G. VIEILLE-
DENT. 2014. Improved Allometric Models to Estimate the Above-
ground Biomass of Tropical Trees. Global Change Biology 20(10):
31773190. doi:10.1111/gcb.12629.
CIAIS, P., A. BOMBELLI,M.WILLIAMS,S.L.PIAO,J.CHAVE,C.M.RYA N,M.
HENRY,P.BRENDER,AND R. VALENTINI. 2011. The carbon balance of
Africa: Synthesis of recent research studies. Philos Trans A Math Phys
Eng Sci 369: 20382057.
Congo basin forest partnership. 2006. The Forests of the Congo Basin. State of
the Forest 2006. In Congo basin forest partnership (Ed.) 255 pages.
DECHAMPS, R., R. LANFRANCHI,A.LeCOCQ,AND D. SCHWARTZ. 1988. Recon-
stitution denvironnements quaternaires par letude de macrorestes
10 Nieto-Quintano, et al.
vegetaux. (Pays Bateke, R.P. du Congo). Palaeogeogr. Palaeoclimatol.
Palaeoecol. 66: 3344.
DESCOIGNS, B. 1960. Rapport botanique preliminaire sur la Cuvette congolaise
(Republique du Congo). Rapport detude n°4, p. 15. ORSTOM.
DESCOIGNS, B. 1972. Notes de phytoecologie equatoriale les steppes loussekes
du plateau Bateke (Congo). Adansonia 2: 569584.
D
ORGELOH, W. G. 2002. Calibrating a disc pasture meter to estimate above-
ground standing biomass in Mixed Bushveld, South Africa. Afr. J.
Ecol. 40: 100102.
DUVIGNEAUD, P. 1949. Les Savanes du Bas-Congo: essai de phytosociologie
topographique. Les Presses de Lejeunia,Liege.
DUVIGNEAUD, P. 1953a. La Flore et la vegetation du Congo Meridional. Lejeu-
nia 16: 95124.
DUVIGNEAUD, P. 1953b. Les formations herbeuses (savanes et steppes) du
Congo meridional. Les Naturalistes Belges 34: 6675.
ELENGA, H., D. SCHWARTZ,AND A. VINCENS. 1994. Pollen evidence of late
Quaternary vegetation and inferred climate changes in Congo. Palaeo-
geogr. Palaeoclimatol. Palaeoecol. 109: 345356.
FAVIER,C.,J.CHAVE,A.FABING,D.SCHWARTZ,AND M. A. DUBOIS. 2004.
Modelling forest-savanna mosaic dynamics in man-inuenced environ-
ments: Effects of re, climate and soil heterogeneity. Ecol. Model.
171: 85102.
FAYOLLE, A., M. D. SWAINE,J.ALEMAN,A.F.AZIHOU, and D. BAUMAN M. te
BEEST,E.CHIDUMAYO,J.CROMSIGT,M.FINCKH,F.MAIATO,P.GON-
ÇALVES,J.GILLET,A.GOREL,A.HICK,R.HOLDO,B.KIRUNDA,G.
MAHY,I.MCNICOL,C.M.RYAN,R.REVERMANN,A.PLUMPTRE,R.
PRITCHARD,P.NIETO-QUINTANO,C.B.SCHMIDT,J.SEGHIERI,T.SWEM-
MER,H.TELILA,AND E. WOOLLEN. 2018. A sharp oristic discontinuity
revealed by the biogeographic regionalization of African savannas.
Under Review (Journal of Biogeography)
FORESTA, H. 1990. Origine et evolution des savanes intramayombiennes (R.P.
du Congo). II. Apports de la botanique forestiere. Paysages quater-
naires de lAfrique centrale atlantique, pp. 326335. Orstom, Paris.
FYNN, R. W. S., C. D. MORRIS,AND T. J. EDWARDS. 2004. Effect of burning
and mowing on grass and forb diversity in a long-term grassland
experiment. Appl. Veg. Sci. 7: 110.
GIGAUD, M. 2012. Etat des jacheres forestieres du Plateau Bateke et, possi-
bilite de les restaurer par Regeneration Naturelle Assistee (RNA) Pro-
jet Makala, Republique Democratique du Congo. MSc Dissertation.
Environnement et Societes. UniversitedOrleans, Montpellier.
GIRAUDOUX, P. 2017. pgirmess: Data analysis in ecology. R Package Version 1(6): 7.
HADDON, I. G. 2000. Kalahari group sediments. In T. C. Partridge, and R. R.
Maud (Eds.). The cenozoic of southern Africa, oxford monographs
on geology and geophysics, vol 40, pp. 173181. Oxford University
Press, New York.
HALL,D.O.,AND J. M. O. SCURLOCK. 1991. Climate change and productivity
of natural grasslands. Ann. Bot. 67: 4955.
HARRIS, I., P. D. JONES,T.J.OSBORN,AND D. H. LISTER. 2014. Updated high-
resolution grids of monthly climatic observations the CRU TS3.10
Dataset. Int. J. Climatol., 34: 623642.
HIGGINS, S. I., W. J. BOND,AND W. S. W. T ROLLOPE. 2000. Fire, resprouting
and variability: A recipe for grass-tree coexistence in savanna. J. Ecol.
88: 213229.
HOARE, A. L. 2007. The use of non-timber forest products in the Congo
Basin: Constraints and Opportunities. In The Rainforest Foundation
(Ed.). London, United Kingdom. 53 pages.
HSIEH, T. C., K. H. MA,AND A. CHAO. 2016. iNEXT: An R package for rar-
efaction and extrapolation of species diversity (Hill numbers). Methods
Ecol. Evol. 7: 14511456.
IFO, S. A. 2017. Variation of d13C and soil organic carbon dynamics in the
savannah of Plateau Bateke, Congo Bassin. International Journal of
Scientic & Technology Research 6(01). 181185.
IUCN, and UNEP. 2015. World Database on Protected Areas (WDPA).
UNEP-WCMC, Cambridge, UK.
JACKSON, R. B., J. CANADELL,J.R.EHLERINGER,H.A.MOONEY,O.E.SALA,
AND E. D. SCHULZE. 1996. A global analysis of root distributions for
terrestrial biomes. Oecologia 108: 389411.
KOECHLIN, J. 1960. La vegetation des savanes du sud de la Republique du Congo.
PhD Dissertation. Faculte des Sciences de Montpellier, Montpellier.
LACHENAUD, O. 2009. The vascular plant ora of the Republic of Congo:
New records. Syst. Geogr. Plants 79: 199214.
LOKEGNA, D. 2015. Biomasse racinaire des arbustes des savanes des Plateaux
Tekes. MSc Dissertation. Ecole Nationale Superieure dAgronomie et
de Foresterie. Universite Marien Ngouabi, Brazzaville.
van der MAESEN,J.,AND G. M. WALTERS. 2011. Novitates Gabonenses 77: A
new Eriosema (Leguminosae-Papilionoideae) from Gabon and adja-
cent Congo. Plant Ecology and Evolution 144: 101105.
MAKANY, L. 1973. Recherches sur la vegetation des plateaux Batekes (Congo)
PhD Dissertation. Universite Pierre et Marie Curie (Paris).
MALEY, J. 1991. The African rain forest vegetation and palaeoenvironments
during late quaternary. Clim. Change. 19: 7998.
MALEY, J. 2001. La destruction catastrophique des for^ets dAfrique centrale
survenue il y a environ 2500 ans exerce encore une inuence majeure
sur la repartition actuelle des formations vegetales. Syst. Geogr. Plants
71: 777796.
MALEY,J.,AND K. WILLIS. 2010. Did a savanna corridor open up across the
Central African Forests 2500 years ago? CoForChange Newsletters
(2). 5 pages.
MAMPOUYA, E. 2015. Biodiversite et variabilite de la densite du bois des
arbustes de savane dans les environs du village M^ah (Plateaux
TEKE, Republique du Congo). MSc Dissertation. Ecole Nationale
Superieure dAgronomie et de Foresterie. Universite Marien
Ngouabi, Brazzaville.
MASOCHA, M., A. K. SKIDMORE,X.POSHIWA,AND H. H. T. PRINS. 2011. Fre-
quent burning promotes invasions of alien plants into a mesic African
savanna. Biol. Invasions 13: 16411648.
MAURIN, O., T. J. DAVIES,J.E.BURROWS,B.H.DARU,K.YESSOUFOU,A.M.
MUASYA, M. van der BANK,AND W. J. B OND. 2014. Savanna re and
the origins of the underground forestsof Africa. New Phytol. 204:
201214.
MENAUT, J. C. 1983. The vegetation of African Savannas. Tropical Savannas.
Ecosystems of the World 13: 109149.
MILLS, A. J., A. V. MILEWSKI,M.V.FEY,A.GR
ONGR
OFT,A.PETERSEN,AND C.
SIRAMI. 2013. Constraint on woody cover in relation to nutrient con-
tent of soils in western southern Africa. Oikos 122: 136148.
NAMRI, M. 1996. Les stocks de carbone des sols du Congo: bilan spatial et
recherche des facteurs de repartition. MSc Dissertation. UFR de
Geographie. Universite Louis Pasteur, Strasbourg.
NIETO-QUINTANO, P., E. T. A. MITCHARD,R.ODENDE,M.A.BATSA MOU-
WEMBE,T.RAYDEN,AND C. M. RYAN. 2018. Data from: The mesic
savannas of the Bateke Plateau: carbon stocks and oristic composi-
tion. Dryad Digital Repository. https://doi.org/10.5061/dryad.
2122768.
NSONGOLA, G., L. OKANDZA,J.OMBANI,AND T. KING. 2006. Liste illustree des
plantes des Reserves Lesio-Louna et Leni, edition 1.1. In John Aspinall
Foundation/CERVE (Ed.). Report. Brazzaville, Congo. 48 pages.
ODENDE, R. 2016. Etude comparative de la ore des savanes des reserves de
la Leni et de la Lesio-Louna dans les Plateaux Tekes. MSc Disserta-
tion. Universite Marien Ngouabi.
OKSANEN, J., F. G. BLANCHET,R.KINDT,P.LEGENDRE,P.R.MINCHIN,R.B.
OHARA,G.L.SIMPSON,P.SOLYMOS,M.H.H.STEVENS,AND H. WAGNER.
2013. vegan: Community Ecology Package, R package version 2.0-10.
OLSON, D. M., E. DINERSTEIN,E.D.WIKRAMANAYAKE,N.D.BURGESS,G.V.
N. POWELL,E.C.UNDERWOOD,J.A.DAMICO,I.ITOUA,H.E.STRAND,
J. C. MORRISON,C.J.LOUCKS,T.F.ALLNUTT,T.H.RICKETTS,Y.KURA,
J. F. LAMOREUX,W.W.WETTENGEL,P.HEDAO,AND K. R. KASSEM.
2001. Terrestrial ecoregions of the world: A new map of life on Earth.
Bioscience 51: 933938.
Carbon and Floristics of the Bateke Plateau 11
OSLISLY, R., L. WHITE,I.BENTALEB,C.FAVIER,M.FONTUGNE,J.F.GILLET,
AND D. SEBAG. 2013. Climatic and cultural changes in the west Congo
Basin forests over the past 5000 years. Philos. Trans. R. Soc. Lond. B
Biol. Sci. 368: 20120304.
R Core Team. 2015. R Foundation for Statistical Computing. R: A Language
and Environment for Statistical Computing, Vienna, Austria.
RAYDEN, T., N. MABIALA,A.TSOUMOU,AND L. ESCOUFLAIRE. 2014. Bateke
Leni Landscape Project Annual report. In W. C. S. Carpe (Ed.). V2.
27 pages.
REVERMANN, R., F. M. GONC
ßALVES,A.L.GOMES,AND M. FINCKH. 2017.
Woody species of the miombo woodlands and geoxylic grasslands of
the cusseque area, south-central Angola. Check List, The Journal of
Biodiversity Data, 13(1) Article 2030. 110.
ROBYNS, W. 1949. Flore du Congo Belge et du Ruanda-Urundi. Bulletin du
Jardin botanique de l
Etat a Bruxelles 19.
RYAN, C. M. 2009. Carbon Cycling, Fire and Phenology in a Tropical Savanna
Woodland in Nhambita, Mozambique. PhD Dissertation. University
of Edinburgh.
RYAN, C. M., R. PRITCHARD,I.MCNICOL,M.OWEN,J.A.FISHER,AND C. LEH-
MANN. 2016. Ecosystem services from southern African woodlands
and their future under global change. Philos. Trans. R. Soc. Lond. B
Biol. Sci. 371: 20150312.
RYAN, C. M., M. WILLIAMS,AND J. GRACE. 2011. Above- and belowground car-
bon stocks in a miombo woodland landscape of mozambique.
Biotropica 43: 423432.
SANKARAN, M., N. P. HANAN,R.J.SCHOLES,J.RATNAM,D.J.AUGUSTINE,B.S.
CADE,J.GIGNOUX,S.I.HIGGINS,X.LeROUX,F.LUDWIG,J.ARDO,F.
BANYIKWA,A.BRONN,G.BUCINI,K.K.CAYLOR,M.B.COUGHENOUR,
A. DIOUF,W.EKAYA,C.J.FERAL,E.C.FEBRUARY,P.G.H.FROST,P.
HIERNAUX,H.HRABAR,K.L.METZGER,H.H.T.PRINS,S.RINGROSE,
W. S EA,J.TEWS,J.WORDEN,AND N. ZAMBATIS. 2005. Determinants of
woody cover in African savannas. Nature 438: 846849.
SCHOLES, R. J. 1990. The inuence of soil fertility on the ecology of southern
African dry savannas. J. Biogeogr. 17: 415419.
SCHOLES,R.J.,AND S. R. ARCHER. 1997. Tree-grass interactions in Savannas.
Annu. Rev. Ecol. Evol. Syst. 28: 517544.
SCHOLES, R. J., P. R. DOWTY,K.CAYLOR,D.A.B.PARSONS,P.G.H.FROST,
AND H. H. SHUGART. 2002. Trends in savanna structure and composi-
tion along an aridity gradient in the Kalahari. J. Veg. Sci. 13: 419428.
SCHWARTZ, D. 1988. Some podzols on Bateke sands and their origins, Peoples
Republic of Congo. Geoderma 43: 229247.
SCHWARTZ, D. 1992. Climatic drying about 3000 BP and Bantu expansion in
Atlantic Central Africa: Some reections. Bulletin - Societe Geologique
de France 163: 353361.
SCHWARTZ, D., R. DECHAMPS,H.ELENGA,R.LANFRANCHI,A.MARIOTTI,AND
A. VINCENS. 1995. Les savanes du Congo: Une vegetation specique
de lholocene superieur. 2e Symposium de Palynologie africaine,
Tervuren (Belgique) Publ. Occas. CIFEG, 1995/31, Orleans, CIFEG,
99108.
SCHWARTZ,D.,AND M. NAMRI. 2002. Mapping the total organic carbon in the
soils of the Congo. Glob Planet Change 33: 7793.
SCURLOCK,J.M.O.,AND D. O. H ALL. 1998. The global carbon sink: A grass-
land perspective. Glob. Change Biol. 4: 229233.
SITA,P.,AND J. M. MOUTSAMBOTE. 1988. Catalogue des plantes vasculaires du
Congo. ORSTOM, Centre dEtudes sur les Ressources Vegetales,
Brazzaville, Congo.
SMITH, M. D., A. K. KNAPP,S.L.COLLINS,D.E.BURKEPILE,K.P.KIRKMAN,
S. E. KOERNER,D.I.THOMPSON,J.M.BLAIR,C.E.BURNS,S.EBY,E.
J. FORRESTEL,R.W.S.FYNN,N.GOVENDER,N.HAGENAH,D.L.
HOOVER,AND K. R. WILCOX. 2016. Shared drivers but divergent eco-
logical responses: Insights from long-term experiments in Mesic
Savanna Grasslands. Bioscience 66: 666682.
SMITH,M.D.,B.W.VanWILGEN,C.E.BURNS,N.GOVENDER,A.L.F.POTGI-
ETER,S.ANDELMAN,H.C.BIGGS,J.BOTHA,AND W. S . W. T ROLLOPE.
2013. Long-term effects of re frequency and season on herbaceous
vegetation in savannas of the Kruger National Park, South Africa. J.
Plant Ecol. 6: 7183.
SOSEF, M. S. M. E. A. 2006. The Checklist of Gabonese Vascular Plants.
SOSEF, M. S. M., G. DAUBY,A.BLACH-OVERGAARD,X.VAN DER BURGT,L.
CATARINO,T.DAMEN,V.DEBLAUWE,S.DESSEIN,J.DRANSFIELD,V.
DROISSART,M.C.DUARTE,H.ENGLEDOW,G.FADEUR,R.FIGUEIRA,
R. E. GEREAU,O.J.HARDY,D.J.HARRIS,J.DE HEIJ,S.JANSSENS,
Y. KLOMBERG,A.C.LEY,B.A.MACKINDER,P.MEERTS,J.L.VAN
DE POEL,B.SONK
E,T.ST
EVART,P.STOFFELEN,J.C.SVENNING,P.
SEPULCHRE,R.ZAISS,J.J.WIERINGA,AND T. L. P. COUVREUR. 2017.
Exploring the oristic diversity of tropical Africa. BMC Biol. 15:15.
123.
STAVER, A. C. 2018. Prediction and scale in savanna ecosystems. New Phytol.
219: 5257.
STAVER,A.C.,S.ARCHIBALD,AND S. A. LEVIN. 2011. The global extent and
determinants of savanna and forest as alternative biome states. Science
334: 230232.
The Plant List. 2013. Version 1. Available at: http://www.theplantlist.org/
(accessed August 2017).
TRAPNELL, C. G. 1959. Ecological results of woodland and burning experi-
ments in northern Rhodisia. J. Ecol. 47: 129168.
VELDMAN, J. W., L. A. BRUDVIG,E.I.DAMSCHEN,J.L.ORROCK,W.B.MAT-
TINGLY
,AND J. L. WALKER. 2014. Fire frequency, agricultural history
and the multivariate control of pine savanna understorey plant diver-
sity. J. Veg. Sci. 25: 14381449.
VELDMAN, J. W., E. BUISSON,G.DURIGAN,G.W.FERNANDES,S.LeSTRADIC,
G. MAHY,D.NEGREIROS,G.E.OVERBECK,R.G.VELDMAN,N.P.
ZALOUMIS,F.E.PUTZ,AND W. J. B OND. 2015. Toward an old-growth
concept for grasslands, savannas, and woodlands. Front. Ecol. Envi-
ron. 13: 154162.
VINCENS, A., D. SCHWARTZ,H.ELENGA,I.REYNAUD-FARRERA,A.ALEXANDRE,
J. BERTAUX,A.MARIOTTI,L.MARTIN,J.D.MEUNIER,F.NGUETSOP,M.
SERVANT,S.SERVANT-VILDARY,AND D. WIRRMANN. 1999. Forest
response to climate changes in Atlantic Equatorial Africa during the
last 4000 years BP and inheritance on the modern landscapes. J. Bio-
geogr. 26: 879885.
WALTERS, G. 2007. Fire Primer for the Bateke Plateaux, Central Africa. In
Missouri Botanical Garden, USA. Internal report to the Rufford
Foundation. 42 pp.
WALTERS, G. 2010a. The Land Chiefs embers: ethnobotany of Batekere
regimes, savanna vegetation and resource use in Gabon. PhD Disser-
tation. University College London.
WALTERS, G. 2010b. Savanna burning yesterday and today in Gabons
Bateke Plateaux: Foraging-res and ecosystem effects. In UCL
(Ed.). 17 pp.
WALTERS, G. 2012. Customary re regimes and vegetation structure in
Gabons Bateke Plateaux. Human Ecology 40: 943955.
WALTERS, G., A. BRADLEY,AND R. NIANGADOUMA. 2006. Floristics of Gabons
Bateke Plateaux: Guineo-Congolian plants on Kalahari Sands. In Tax-
onomy and Ecology of African Plants, their Conservation and Sustain-
able Use, S. A. Gazanfar, and H. J. Beentje, eds., London: Royal
Botanic Gardens Kew, pp. 259266.
WALTERS, G., I. PARMENTIER,AND T. ST
EVART. 2013. Diversity and conservation
value of Gabons savanna and inselberg open vegetation: An initial
gap analysis. Plant Ecology and Evolution, 145(1), 4654.
WHITE, F. 1977. The underground forests of Africa: A preliminary review.
GardensBulletin, Singapore 29: 5771.
WHITE, F. 1979. The Guineo-Congolian Region and Its Relationships to Other
Phytochoria. Bulletin du Jardin Botanique National de Belgique/Bul-
letin van de Nationale Plantentuin van Belgie 49: 1155.
WHITE, F. 1983. The vegetation of Africa, a descriptive memoir to accompany
the UNESCO/AETFAT/UNSO vegetation map of Africa, Paris.
WIERINGA,J.J.,AND M. S. M. SOSEF. 2011. The applicability of relative oristic
resemblance to evaluate the conservation value of protected areas.
Plant Ecology and Evolution 144: 242248.
YOK-
12 Nieto-Quintano, et al.
A, J., J. J. L OUMETO,J.VOUIDIBIO,B.AMIAUD,AND D. EPRON. 2010.
Inuence du sol sur la repartition et la production de la phytomasse
des savanes de la Cuvette congolaise. Geo EcoTrop 34: 6374.
YOKA, J., J. J. L OUMETO,J.VOUIDIBIO,AND D. EPRON. 2013. Productivite
herbacee des savanes de la Cuvette congolaise (Congo-Brazzaville).
Afrique Science 9: 89101.
ZALOUMIS,N.P.,AND W. J . B OND. 2016. Reforestation or conservation? The
attributes of old growth grasslands in South Africa. Philos. Trans. R.
Soc. Lond. B Biol. Sci. 371(1703). 9 pages.
ZANNE, A. E., G. LOPEZ-GONZALEZ,D.A.COOMES,J.ILIC,S.JANSEN,S.L.
LEWIS,R.B.MILLER,N.G.SWENSON,M.C.WIEMANN,AND J. CHAVE.
2009. Global Wood Density Database. Dryad.
Carbon and Floristics of the Bateke Plateau 13
... In current practice, the size threshold above which tree stems are measured and counted as new recruits varies greatly. In some systems, trees rarely exceed 10 cm DBH (Nieto-Quintano et al., 2018), and so a smaller threshold is needed to gain information on their dynamics. However, small size thresholds may not produce useful information on population dynamics when turnover rates (mortality and recruitment) are very high in small size classes, unless census intervals are short, for example, 1-2 years. ...
... Each plot is shown by a single line, colored according to the site. Cyan = DR Congo, protected wet miombo (Muledi et al., 2018; Pink = Tanzania dry miombo ; Black = Angolan dry miombo/Baikiaea (Godlee et al., 2020); Green = Mozambican dry miombo and mixed woodland ; Blue = South African Mimosoid savannas (Scholes et al., 2001); Red = Congolian Beteke savanna (Nieto-Quintano et al., 2018) . Note that for clarity the figure has been clipped to 1,000 stems and 40 species. ...
... Nieto-Quintano et al., 2018;Pritchard et al., 2019). ...
Article
Full-text available
The sustainable management of the southern African woodlands is closely linked to the livelihoods of over 150 M people. Findings from the Socio‐Ecological Observatory for the Southern African Woodlands (SEOSAW) will underpin the sustainability of two of the largest industries on the continent: woodfuels and timber. SEOSAW will also improve our understanding of how human use shapes the biogeography and functioning of these ecosystems. The sustainable management of the southern African woodlands is closely linked to the livelihoods of over 150 M people. Findings from the Socio‐Ecological Observatory for the Southern African Woodlands (SEOSAW) will underpin the sustainability of two of the largest industries on the continent: woodfuels and timber. SEOSAW will also improve our understanding of how human use shapes the biogeography and functioning of these ecosystems. Here we describe a new network of researchers and long‐term, in situ, measurements that will characterize the changing socio‐ecology of the woodlands of southern Africa. These woodlands encompass the largest savanna in the world, but are chronically understudied, with few long‐term measurements. A network of permanent sample plots (PSPs) is required to: (a) address management issues, particularly related to sustainable harvesting for energy and timber; (b) understand how the woodlands are responding to a range of global and local drivers, such as climate change, CO2 fertilization, and harvesting; and (c) answer basic questions about biogeography, ecosystem function, and the role humans play in shaping the ecology of the region. We draw on other successful networks of PSPs and adapt their methods to the specific challenges of working in southern African woodlands. In particular we suggest divergences from established forest monitoring protocols that are needed to (a) adapt to a high level of ecosystem structural diversity (from open savanna to dry forest); (b) quantify the chronic disturbances by people, fire, and herbivores; (c) quantify the diversity and function of the understory of grasses, forbs, and shrubs; (d) understand the life histories of resprouting trees; and (e) conduct work in highly utilized, human‐dominated landscapes. We conclude by discussing how the SEOSAW network will integrate with remote sensing and modeling approaches. Throughout, we highlight the challenges inherent to integrating work by forest and savanna ecologists, and the wide range of skills needed to fully understand the socio‐ecology of the southern African woodlands.
... In current practice, the size threshold above which tree stems are measured and counted as new recruits varies greatly. In some systems, trees rarely exceed 10 cm DBH (Nieto-Quintano et al., 2018), and so a smaller threshold is needed to gain information on their dynamics. However, small size thresholds may not produce useful information on population dynamics when turnover rates (mortality and recruitment) are very high in small size classes, unless census intervals are short, for example, 1-2 years. ...
... Each plot is shown by a single line, colored according to the site. Cyan = DR Congo, protected wet miombo (Muledi et al., 2018; Pink = Tanzania dry miombo ; Black = Angolan dry miombo/Baikiaea (Godlee et al., 2020); Green = Mozambican dry miombo and mixed woodland ; Blue = South African Mimosoid savannas (Scholes et al., 2001); Red = Congolian Beteke savanna (Nieto-Quintano et al., 2018) . Note that for clarity the figure has been clipped to 1,000 stems and 40 species. ...
... Nieto-Quintano et al., 2018;Pritchard et al., 2019). ...
Article
• Here we describe a new network of researchers and long-term, in situ, measurements that will characterize the changing socio-ecology of the woodlands of southern Africa. These woodlands encompass the largest savanna in the world, but are chronically understudied, with few long-term measurements. • A network of permanent sample plots (PSPs) is required to: (a) address management issues, particularly related to sustainable harvesting for energy and timber; (b) understand how the woodlands are responding to a range of global and local drivers, such as climate change, CO2 fertilization, and harvesting; and (c) answer basic questions about biogeography, ecosystem function, and the role humans play in shaping the ecology of the region. • We draw on other successful networks of PSPs and adapt their methods to the specific challenges of working in southern African woodlands. In particular we suggest divergences from established forest monitoring protocols that are needed to (a) adapt to a high level of ecosystem structural diversity (from open savanna to dry forest); (b) quantify the chronic disturbances by people, fire, and herbivores; (c) quantify the diversity and function of the understory of grasses, forbs, and shrubs; (d) understand the life histories of resprouting trees; and (e) conduct work in highly utilized, human-dominated landscapes. • We conclude by discussing how the SEOSAW network will integrate with remote sensing and modeling approaches. Throughout, we highlight the challengesinherent to integrating work by forest and savanna ecologists, and the wide range of skills needed to fully understand the socio-ecology of the southern African woodlands.
... Nested plots are not normally recommended for use with remote sensing, but are common in savanna landscapes in order to allow robust assessments of the biomass of more homogeneous, small-size vegetation (grass, seedlings, shrubs) which need distributed small sub-plots, within the large plots needed to estimate biomass of distributed trees. For example, in the Bateke savanna landscape of the Republic of Congo, typified by very low biomass values (6.5 Mg C/ha including above and below-ground biomass of trees, shrubs and grass), four 25 ha plots were set up and further analysis of the data found that a plot size of at least 10 hectares were needed to provide a good estimate of the mean tree biomass, due to the clumpiness of the trees (Nieto-Quintano et al., 2018). ...
... • If woody biomass is the focus of the study, then only trees should be measured. But in some landscapes shrub and especially grass biomass may be significant: grass represented over half the biomass in the Bateke landscape studied by Nieto-Quintano (2018). For shrubs, see the recommendations for Drylands (A.3.5). ...
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Full-text available
the full text can be found at: https://lpvs.gsfc.nasa.gov/PDF/CEOS_WGCV_LPV_Biomass_Protocol_2021_V1.0.pdf
... Nested plots are not normally recommended for use with remote sensing, but are common in savanna landscapes in order to allow robust assessments of the biomass of more homogeneous, small-size vegetation (grass, seedlings, shrubs) which need distributed small sub-plots, within the large plots needed to estimate biomass of distributed trees. For example, in the Bateke savanna landscape of the Republic of Congo, typified by very low biomass values (6.5 Mg C/ha including above and below-ground biomass of trees, shrubs and grass), four 25 ha plots were set up and further analysis of the data found that a plot size of at least 10 hectares were needed to provide a good estimate of the mean tree biomass, due to the clumpiness of the trees (Nieto-Quintano et al., 2018). ...
... • If woody biomass is the focus of the study, then only trees should be measured. But in some landscapes shrub and especially grass biomass may be significant: grass represented over half the biomass in the Bateke landscape studied by Nieto-Quintano (2018). For shrubs, see the recommendations for Drylands (A.3.5). ...
... In current practice, the size threshold above which tree stems are measured and counted as new recruits varies greatly. In some systems, trees rarely exceed 10 cm DBH (Nieto-Quintano et al., 2018), and so a smaller threshold is needed to gain information on their dynamics. However, small size thresholds may not produce useful information on population dynamics when turnover rates (mortality and recruitment) are very high in small size classes, unless census intervals are short, for example, 1-2 years. ...
... Each plot is shown by a single line, colored according to the site. Cyan = DR Congo, protected wet miombo (Muledi et al., 2018; Pink = Tanzania dry miombo ; Black = Angolan dry miombo/Baikiaea (Godlee et al., 2020); Green = Mozambican dry miombo and mixed woodland ; Blue = South African Mimosoid savannas (Scholes et al., 2001); Red = Congolian Beteke savanna (Nieto-Quintano et al., 2018) . Note that for clarity the figure has been clipped to 1,000 stems and 40 species. ...
Article
Full-text available
A network to understand the changing socio-ecology of the southern African woodlands (SEOSAW): Challenges, benefits, and methods The SEOSAW partnership* This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. The sustainable management of the southern African woodlands is closely linked to the livelihoods of over 150 M people. Findings from the Socio-Ecological Observatory for the Southern African Woodlands (SEOSAW) will underpin the sustainability of two of the largest industries on the continent: woodfuels and timber. SEOSAW will also improve our understanding of how human use shapes the biogeography and functioning of these ecosystems. Summary • Here we describe a new network of researchers and long-term, in situ, measurements that will characterize the changing socio-ecology of the woodlands of southern Africa. These woodlands encompass the largest savanna in the world, but are chronically understudied, with few long-term measurements. • A network of permanent sample plots (PSPs) is required to: (a) address management issues, particularly related to sustainable harvesting for energy and timber; (b) understand how the woodlands are responding to a range of global and local drivers, such as climate change, CO 2 fertilization, and harvesting; and (c) answer basic questions about biogeography, ecosystem function, and the role humans play in shaping the ecology of the region. • We draw on other successful networks of PSPs and adapt their methods to the specific challenges of working in southern African woodlands. In particular we suggest divergences from established forest monitoring protocols that are needed to (a) adapt to a high level of ecosystem structural diversity (from open savanna to dry forest); (b) quantify the chronic disturbances by people, fire, and herbivores; (c) quantify the diversity and function of the understory of grasses, forbs, and shrubs; (d) understand the life histories of resprouting trees; and (e) conduct work in highly utilized, human-dominated landscapes. • We conclude by discussing how the SEOSAW network will integrate with remote sensing and modeling approaches. Throughout, we highlight the challenges
... In Central Africa, savanna ecosystems and their floral diversity in relation to fire remain underexplored; studies focus on carbon stocks and biomass (Batsa Mouwembe et al. 2017;Ifo et al. 2018;Nieto-Quintano et al. 2018), forest recovery (Deklerck et al. 2019), or the forest-savanna interface (Cardoso et al. 2018). In general, research on African savanna forb floras in relation to fire constitutes a significant knowledge gap, with most studies focusing on grasses and trees, and dry savannas (Siebert and Dreber 2019). ...
Article
Full-text available
Background and aims – Old-growth savannas in Africa are impacted by fire, have endemic and geoxylic suffrutices, and are understudied. This paper explores the Parc National des Plateaux Batéké (PNPB) in Gabon and the impact of fire on its flora to understand if it is an old-growth savanna. It presents 1) a vascular plant checklist, including endemic species and geoxylic suffrutices and 2) an analysis of the impact of fire on the savanna herbaceous flora, followed by recommendations for fire management to promote plant diversity. Material and methods – 1,914 botanical collections from 2001–2019 collected by the authors and others were extracted from two herbaria databases in 2021 to create the checklist. The impact of fire was explored through a three season plot-based inventory of plant species (notably forbs and geoxylic suffrutices) in five annually, dry-season burned study areas located at 600 m in elevation. A two-factor ANOVA was conducted across two burn treatments and three season treatments. Key results – The area has a vascular flora of 615 taxa. Seven species are endemic to the Plateaux Batéké forest-savanna mosaic. Seventeen species are fire-dependent geoxylic suffrutices, attesting to the ancient origins of these savannas. Burning promotes fire-dependent species. Conclusion – The PNPB aims to create a culturally-adapted fire management plan. The combination of customary fire and fire-adapted species in the savanna creates a unique ancient forest-savanna mosaic in Central Africa that merits protection while recognising the role that the Batéké-Alima people have in shaping and governing this landscape.
... Obtaining accurate estimates of BGB is recognized as essential for determining its contribution to carbon storage (Chamberlain et al. 2013), and thus required for reporting to the United Nations Framework Convention on Climate Change and REDDþ. So far, most inventories have used an average root-to-shoot ratio and allometric equations to estimate BGB for several purposes such as carbon accounting (Chidumayo 2013, Nieto-Quintano et al. 2018, Ryan et al. 2010. However, none of these methods can be applied to suffrutex grasslands due to the great difference between above and belowground organs (Robertson 2005). ...
Article
Full-text available
Despite its importance for carbon stocks accounting, belowground biomass (BGB) has seldom been measured due to the methodological complexity involved. In this study, we assess woody BGB and related carbon stocks, soil properties and human impact on two common suffrutex grasslands ( Brachystegia - and Parinari grasslands) on the Angolan Central Plateau. Data on BGB was measured by direct destructive sampling. Soil samples were analysed for select key parameters. To investigate vegetation dynamics and human impact, we used Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) and fire data retrieved via Google Earth Engine. Mean belowground woody biomass of sandy Parinari grasslands was 17 t/ha and 44 t/ha in ferralitic Brachystegia grasslands of which 50% correspond to carbon stocks. As such, the BGB of Brachystegia grasslands almost equals the amount of aboveground biomass (AGB) of neighbouring miombo woodlands. Almost the entire woody BGB is located in the top 30 cm of the soil. Soils were extremely acid, showing a low nutrient availability. Both grassland types differed strongly in EVI and fire seasonality. The Parinari grasslands burnt almost twice as frequent as Brachystegia grasslands in a 10-year period. Our study emphasizes the high relevance of BGB in suffrutex grasslands for carbon stock accounting.
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Une étude sur la variabilité spatiale du stock de carbone organique et de l'azote totale a été faite dans les savanes des plateaux Tékés précisément dans deux sites le plateau de Mbé (réserve de Lésio-Louna) et le plateau de Nsa (réserve de Faune de Léfini). L'objectif général de l'étude était de déterminer les causes de la variabilité spatiale du carbone organique ainsi que de l'azote totale horizons 0-5 et 5-20 cm. Les teneurs en carbone totale ont été déterminées par oxydation du carbone en un milieu acide; la teneur en azote total par la méthode de Kjeldahl, et la densité apparente par la méthode du cylindre. Les résultats nous indiquent que l'horizon h1 (5-20 cm) possède un stock de carbone plus important que l'horizon h0 (0-5 cm) dans les deux sites. Dans le site de Lésio-Louna, ce stock a été évalué à 1,16 kg.m-2 pour l'horizon h1 contre 0,44 kg.m-2 pour l'horizon h0, et dans le site de Léfini, ce stock a été évalué à 1,24 kg.m-2 pour l'horizon h1 contre 0,51 kg.m-2 pour l'horizon h0. De ces résultats, Il en ressort que la somme des stocks de carbone organique du sol pour l'horizon 0-20 cm dans cet écosystème est de 12,80 kg.m-2 pour Lésio-Louna et 14,03 kg.m-2 pour Léfini. Les résultats de cette étude montrent l'existence d'une très grande variabilité spatiale des stocks de carbone organique du sol à l'échelle de l'hectare. La densité à l'hectare des arbustes dans les parcelles pourrait être le facteur qui influence le plus sur ces stocks de carbone du sol à l'échelle de la parcelle. Mots-clés : stock de carbone du sol, plateau Batéké, savane arbuste. Abstract Spatial variability of soil organic carbon stocks of the savannah into the sanctuary of Lesio Louna and of Lefini, plateaux Tékés, Republic of Congo A study on the spatial variability of the soil organic stock and total nitrogen was done in savanna of the plateau Bateké precisely in two sites the " plateau de Mbé " (sanctuary of Lésio-Louna) and the plateau de Nsa (sanctuary of Fauna of Léfini). The general aim of the study was to determine the causes of this spatial variability of the soil organic carbon and of total nitrogen at the horizons 0-5 and 5-20 cm. The percentages of carbon total were determined by oxidation of carbon of an acid medium; total nitrogen content by the method of Kjeldahl, and the soil density by the method of the cylinder. The results revealed to us that the 298 Afrique SCIENCE 13(3) (2017) 297-307 Marcelle Armande BATSA MOUWEMBE et al. horizon h1 (5-20 cm) had a carbon stock more significant than the horizon h0 (0-5 cm) in the two sites. In the site of Lésio-Louna, this stock was 1.16 kg.m-2 for the horizon h1, 0.44 kg.m-2 for the horizon h0. In the site of Léfini, this stock was 1.24 kg.m-2 for the horizon h1, 0.51 kg.m-2 for the horizon h0. Our results revealed that the total of organic carbon stocks of the ground for the horizon 0-20 cm in this ecosystem was of 12,80 kg.m-2 for Lésio-Louna and 14,03 kg.m-2 for Léfini. We noted the existence of a very great spatial variability of soil organic stock within a plot. The variation of shrubs density within hectare, and slope could be the main factors which determine the spatial variability of the soil carbon stock.
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Une étude sur la variabilité spatiale du stock de carbone organique et de l'azote totale a été faite dans les savanes des plateaux Tékés précisément dans deux sites le plateau de Mbé (réserve de Lésio-Louna) et le plateau de Nsa (réserve de Faune de Léfini). L'objectif général de l'étude était de déterminer les causes de la variabilité spatiale du carbone organique ainsi que de l'azote totale horizons 0-5 et 5-20 cm. Les teneurs en carbone totale ont été déterminées par oxydation du carbone en un milieu acide; la teneur en azote total par la méthode de Kjeldahl, et la densité apparente par la méthode du cylindre. Les résultats nous indiquent que l'horizon h1 (5-20 cm) possède un stock de carbone plus important que l'horizon h0 (0-5 cm) dans les deux sites. Dans le site de Lésio-Louna, ce stock a été évalué à 1,16 kg.m-2 pour l'horizon h1 contre 0,44 kg.m-2 pour l'horizon h0, et dans le site de Léfini, ce stock a été évalué à 1,24 kg.m-2 pour l'horizon h1 contre 0,51 kg.m-2 pour l'horizon h0. De ces résultats, Il en ressort que la somme des stocks de carbone organique du sol pour l'horizon 0-20 cm dans cet écosystème est de 12,80 kg.m-2 pour Lésio-Louna et 14,03 kg.m-2 pour Léfini. Les résultats de cette étude montrent l'existence d'une très grande variabilité spatiale des stocks de carbone organique du sol à l'échelle de l'hectare. La densité à l'hectare des arbustes dans les parcelles pourrait être le facteur qui influence le plus sur ces stocks de carbone du sol à l'échelle de la parcelle. Mots-clés : stock de carbone du sol, plateau Batéké, savane arbuste. Abstract Spatial variability of soil organic carbon stocks of the savannah into the sanctuary of Lesio Louna and of Lefini, plateaux Tékés, Republic of Congo A study on the spatial variability of the soil organic stock and total nitrogen was done in savanna of the plateau Bateké precisely in two sites the " plateau de Mbé " (sanctuary of Lésio-Louna) and the plateau de Nsa (sanctuary of Fauna of Léfini). The general aim of the study was to determine the causes of this spatial variability of the soil organic carbon and of total nitrogen at the horizons 0-5 and 5-20 cm. The percentages of carbon total were determined by oxidation of carbon of an acid medium; total nitrogen content by the method of Kjeldahl, and the soil density by the method of the cylinder. The results revealed to us that the 298 Afrique SCIENCE 13(3) (2017) 297-307 Marcelle Armande BATSA MOUWEMBE et al. horizon h1 (5-20 cm) had a carbon stock more significant than the horizon h0 (0-5 cm) in the two sites. In the site of Lésio-Louna, this stock was 1.16 kg.m-2 for the horizon h1, 0.44 kg.m-2 for the horizon h0. In the site of Léfini, this stock was 1.24 kg.m-2 for the horizon h1, 0.51 kg.m-2 for the horizon h0. Our results revealed that the total of organic carbon stocks of the ground for the horizon 0-20 cm in this ecosystem was of 12,80 kg.m-2 for Lésio-Louna and 14,03 kg.m-2 for Léfini. We noted the existence of a very great spatial variability of soil organic stock within a plot. The variation of shrubs density within hectare, and slope could be the main factors which determine the spatial variability of the soil carbon stock.
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The species composition of the vegetation in most regions of Angola has been poorly studied and most studies date back to the pre-independence era. In this study, we provide a detailed account of the woody flora of the Miombo woodlands and geoxylic grasslands of the Cusseque study site of “The Future Okavango” (TFO) project, situated on the Angolan Central Plateau. The checklist is based on a vegetation survey using vegetation plots of 1,000 m² and also includes records from botanical collections made elsewhere at the study site. In total, we documented 154 woody species belonging to 99 genera of 37 plant families in 100 km². The study represents the first comprehensive account of the woody vegetation of the area including all habitats and growth forms.
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